Our broad goal in this project, Electrophysiological Studies of Communication Disorders, is to study the complementary roles of biological constraints and experience in setting up functionally- specialized neural systems for normal speech and language, and to identify significant variations in this process in children who are at risk for language impairment. To this end we will study changes in brain organization associated with major milestones in language development, and examine the effects of early neurological, metabolic, and/or behavioral abnormalities, on the development of functional specialization for language within and between the two hemispheres. The populations to be studied will include "late talkers" (in collaboration with Project 1), children with early focal brain injury (with Project 2), and children with Williams Syndrome (with Project 3). These populations provide an opportunity to link specific changes in neural development with alterations in the specific sensory and cognitive processes that accompany language acquisition in normal children. We will record event- related potentials from over several brain regions, making comparisons within and between the cerebral hemispheres in a series of studies designed to assess different aspects of linguistic, sensory and cognitive processing at successive stages of language development, from preverbal communication through the emergence of grammar.